/*
 * Copyright 2010-2012 Susanta Tewari. <freecode4susant@users.sourceforge.net>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package commons.util;

import java.util.ArrayList;
import java.util.List;

/**
 * @author Susanta Tewari
 * @since Nov 15, 2011
 */
public class RandomUtil {

    /**
     * Method description
     *
     *
     * @param oldOrder
     * @param <T>
     *
     * @return
     */
    public static <T> List<T> randomBlockReversal(List<T> oldOrder) {

        List<T> result = new ArrayList<>(oldOrder.size());

        // choose 2 end points (i and j) randomly on the length of the order
        int i = (int) (Math.random() * result.size());
        int j = (int) (Math.random() * result.size());

        i = Math.min(i, j);
        j = Math.max(i, j);

        // reverse the block between i and j, including i and j.
        for (int k = i; k <= j; k++) {

            result.set(k, oldOrder.get(j - k + i));
        }

        return result;
    }
}
